1. Field of the Invention
The present invention relates to an extracorporeal blood circulator that is easy to maintain. More particularly, the present invention is directed to an extracorporeal blood circulator having an improved structure for mounting the electrodes of a conductivity meter that monitors the conductivity of a cleaning solution flowing through an adsorbing unit.
2. Description of the Related Art
An extracorporeal blood circulator that provides the basis for the improvement of the present invention, particularly an apparatus of plasma pheresis (a blood plasma cleaner) will be described briefly with reference to FIGS. 2 and 3. In FIG. 2, reference character 1a denotes a blood collecting section for collecting blood from a brachium or the like (not shown) of a patient; and 1b, a blood returning section that returns the blood to the brachium or the like of the patient. The blood collected from the patient is mixed with an anticoagulant supplied from an anticoagulant injecting pump 2, and then conveyed to a blood plasma separator 4 by a blood pump 3. The blood plasma separator 4 separates the conveyed blood into blood plasma and blood cell component, with the blood plasma being conveyed to one of adsorbing units 6a, 6b (here, to the adsorbing unit 6a indicated by the solid line first) and with the blood cell component being conveyed to a mixing section 7.
The adsorbing unit 6a or 6b adsorbs only cholesterol in the blood plasma with a charged adsorbent. The thus treated blood plasma joins with the blood cell component at the mixing section 7, and is returned to the patient from the blood returning section 1b.
Since the adsorption of cholesterol is saturated after the adsorbing unit 6a or 6b has treated some hundreds of milliliters of blood plasma, the adsorbing units must be regenerated before saturation.
In order to regenerate the adsorbing unit 6a, not only the operation of adsorbing cholesterol is continued by the adsorbing unit 6b with the passage switched at a valve 8a to a dotted line A, the adsorbing unit 6b, a valve 8e, and a valve 8f in this sequence, but also a replacement solution within the adsorbing unit 6b is disposed of.
On the other hand, the replacement solution introduced from a replacement solution bag 12 flows to the adsorbing unit 6a via a passage followed by a valve 8c, an activation solution pump 11, a valve 8d, a dotted line C, the adsorbing unit 6a, a valve 8b, and the mixing section 7 in this sequence, so that the treated blood plasma within the adsorbing unit 6a is returned to the body of the patient.
Upon having returned the majority of the treated blood plasma within the adsorbing unit 6a to the body, not only the passage is switched so that an activation solution from an activation solution bag 10 flows via the valve 8c, the activation solution pump 11, the valve 8d, the dotted line C, the adsorbing unit 6a, the valve 8b, a dotted line D, the valve 8f in this sequence to be finally disposed of, but also regeneration of the adsorbing unit 6a is started.
Simultaneously therewith, the valve 8e is switched to a dotted line B on the adsorbing unit 6b side, so that the passage of the adsorbing unit 6b is switched to the mixing section 7 and the treated blood plasma is returned to the body. Further, when the adsorbing unit 6a has been regenerated with a predetermined quantity of activation solution introduced, the valve 8c is switched to the replacement solution bag side, not only causing the replacement solution to drive the activation solution away from the adsorbing unit 6a, but also causing the replacement solution to clean the adsorbing unit 6a and supply the adsorbing unit 6a with the replacement solution until the adsorbing unit 6b performs the treatment up to 600 ml.
On the other hand, the adsorbing unit 6b continuously performs the adsorbing operation under the same condition until the adsorbing unit 6b performs the operation up to 600 ml. Here, only for a period during which some tens of milliliters immediately before the amount of treatment reaches 600 ml, the passage is switched by the valve 8f, so that the replacement solution to be disposed of is caused to flow to the conductivity meter 20a to thereby measure the conductivity of the replacement solution.
The adsorbing units 6b, 6a thereafter repeat the same regenerating operation alternately, switching the passages correspondingly. Conductivity measurements are made to check that the activation solution having high salt concentration is replaced with the replacement solution (0.9% physiological saline). This check is made every time the adsorbing units 6a, 6b are regenerated. Once a medical treatment has been finished, a disinfecting solution is charged into the conductivity meter 20a, so that the electrodes of the conductivity meter 20a which are likely to be contaminated with blood plasma are disinfected.
FIG. 3 is a diagram showing the construction of the front side of a panel of the apparatus of plasma pheresis. The same parts and components as those of FIG. 2 are denoted by the same reference numerals. As shown in FIG. 3, the anticoagulant pump 2, the pumps for blood, blood plasma, activation solution (3, 5, 11), the blood plasma separator 4, the adsorbing units 6a, 6b, a humidifier 14, the respective valves 8, and the tubes for connecting these valves are attached to the front side of the panel, whereas parts contaminated with blood and harmful substance (materies morbi) and the like contained in blood (exemplary parts being the blood plasma separator 4, the adsorbing units 6a, 6b, the tubes through which blood flows, and the like) are disposable. Thus, the disposable parts are designed to be easily attached and detached.
The conductivity meter 20a used for such extracorporeal blood circulator is arranged inside the circulator. FIG. 4 shows the concept of an ordinary conductivity meter. That is, FIG. 4 is a sectional view showing a main portion of an electrode portion of the conductivity meter. Conductivity is measured by dipping the electrodes into a solution to be measured, energizing a dc current of an ac current from a power supply 28 between a pair of electrodes 25a disposed in an insulated sleeve 26a, and measuring the quantity of electricity between the electrodes with an electric meter 29. If ion concentration is low, salt concentration in the cleaning solution flowing through the adsorbing units 6 can be measured since conductivity is proportional to ion concentration.
The conductivity meter is disinfected during every medical treatment. Such disinfecting operation is performed by injecting a disinfecting solution to the electrode portion from the front side of the panel, then leaving the electrode portion as it is for about an hour, and thereafter cleaning the electrode portion with the replacement solution. Therefore, there exists the problem that the disinfecting operation involves a number of steps and is time-consuming.